Disturbances in media flowing within a conduit adversely affect flow meter performance and pump protection by creating, for example, swirl and irregular flow profiles. The resulting errors often exceed the flow meter manufacturer's published accuracy specifications and can lead to cavitation and excessive pump component degradation. Flow conditioning, such as may be accomplished by tube bundles or perforated plates, among others, is known within the prior art to remove swirl and create symmetric and reproducible velocity profiles for media such as liquids, steam, gases, air, vapors, or slurries, and the like, flowing within a conduit. Flow conditioning should also destratify non-uniform media. Velocity profiles that can benefit from flow conditioning include those that are irregular due to disturbances caused by passing through or near obstacles, such as variable valves, bends, blockages, or junctions that create arbitrarily varying flow characteristics. Examples of prior art flow conditioners are described in U.S. Pat. Nos. 4,929,088 and 4,981,368. Additional prior art flow conditioners may have tube bundles, perforated plates, or other baffle arrangements.
FIG. 1 illustrates a prior art flow conditioning device 10 of the type described by U.S. Pat. Nos. 4,929,088 and 4,981,368. This flow conditioner is an assembly that is mounted into a pipe or duct and contains tabs 17 that are angled inwardly in the direction of flow as indicated by arrow A. This device requires a distance of several pipe diameters (typically about six diameters) to properly condition the media flowing within a conduit after passing a plane of flow disturbance 15, FIG. 1 illustrates the six diameters typically required as two distinct distances 12 and 13, each being three diameters. Therefore, media flowing in the duct having flow distortions occurring at a plane of disturbance 15 that is some distance 11 upstream from flow conditioning device 10 can be conditioned by device 10 to have a desired profile when reaching a device such as a pump, or a flow meter 19, or any other device that requires the flowing media to be free of undesired flow profiles and stratification.
There are numerous types of flow distorting devices that can create a plane of flow disturbance 15 including, but not limited to, elbows, bends, junctions, or areas not having a common plane with the conduit. Flowing media needs to travel a distance of several diameters of conduit as shown by distance 13, for the anti-swirl action, vortex generation and annihilation, or settling to take place. This distance is required for the settling to occur downstream of a flow conditioner to insure proper conditioning of the flowing media. Flowing media needs to be properly conditioned before reaching a pump, flow meter, or any other device that requires mixing or destratification. As used herein, “destratification” is the process of mixing either gaseous or liquid substances, or the like, together to eliminate stratified layers of any kind be it temperature, density, concentration, chemical, or diverse media, for example. Further, minimum distorted and uniform flow profiles are very important in pumps where destructive cavitation is a problem, or where stratified or asymmetrical flow rate profiles are present.
Flow conditioning devices, such as shown in FIG. 1, that are used for conduits having sizes above about six inches in diameter are heavy, expensive to ship, and require expertise to handle and install. This situation becomes increasingly more difficult and costly as the size of the conduit, and therefore, the conditioner device, increases in diameter.
Additionally, “floor space” is extremely valuable in particular implementations, such as offshore oil platforms for example. Volume as well as area are important on board ships or aircraft, or inside the containment building in nuclear power plants, all of which have a strong need to minimize straight runs of conduits (“floor space/volume”). In response to this need, the device 20 of FIG. 2 was developed to reduce the problem of long run lengths of conduit that have been required for flow conditioning. This is an illustration of another prior art flow conditioner which at least reduced, but has not completely eliminated, the problem.
Other flow conditioning devices include tube bundles, which do not correct the velocity profile distortion, and perforated plates, which are useful but tend to cause excessive pressure drop, do little mixing, and are not particularly useful in pump protection.